Testing Performance of 10 kW BLDC Motor and LiFePO4 Battery on ITB-1 Electric Car

Prototype

姓名 : 賴弘偉指導老師 : 許毅然

作者 : Agus Purwadi, Jimmy Dozeno, Nana Heryana

Procedia Technology 11 ( 2013 ) 1074 – 1082The 4th International Conference on Electrical Engineering and Informatics (ICEEI 2013)Electrical Power Engineerng, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung, 40123, West Java, Indonesia

Outline Abstract Introduction Electric Vehicle Design Propulsion Motor Used Ionic Lithium LiFePO4Battery Battery Charging-Discharging Test Charging Test Results Discharging Test Results Conclusion References

AbstractThe growing development of Electric vehicle industry due to more greener transportation needs, encouraging ITB as a research based educational institution to give their effort and participation in developing electric city car prototype, especially for Indonesia used.Two fundamental components in the electric car are the electric motor and its energy storage system. The motor used in this ITB-1electric car is brushless dc (BLDC) motor type. A controller will be used to convert the dc source into ac for BLDC motor power source.Voltage is one of the parameters that must be controlled by the battery management system, so that the battery can be protected effectively. In this paper, a 10 kW BLDC motor and its energy storage LiFePO4 battery types, will be evaluated based on their performance result from the tests.

Introduction

Research and development of smart vehicle, such as an electric car, has been started since many years ago in developed countries and still continues now. Indonesia, through its Education and Culture Minsitry and Stated-Own Entreprise Ministry, aims to create its national electric vehicle that can be mass produced and slowly replaced the conventional one. ITB has become one of the several education institutes involved in the design and constructions of this vehicle.Before it is used in the car, the battery must has been tested first to check if it match the specification specified by the manufacturer. This paper will discuss about a study of the performance of BLDC motor and the battery used in ITB electric car prototype.

Electric Vehicle Design

A schematic of an electric car is shown in Fig 1. Main components of an electric are motors as rotating machines, a drive system consists of an inverter and controllers used to convert dc power into ac power and also for adjust the speed and brake, and a battery system as a source of the power.

Electric Car Design

The car is designed for inside city use, hence the range of the car is sufficient for short distance. The car body consist of several main components as shown in fig.2

The car is designed in single platform but for multi-purpose use as shown in fig.3 It has many body design types which is useful in different application.

Here is the specification of the car (see Fig. 4) summarized in Table.1

Propulsion Motor Used

In this prototype car, BLDC motors are used as the propulsion device. This type of motor is also known as electrically commutated motor. It is actually categorized as a synchronous motor supplied from a DC source through an inverter so that the motor will be seen as it is supplied by an AC power source. The inverter output controlled by sensors and electronic controller. BLDC motor has a rotating permanent magnet and static armature just as the synchronous machine. This construction solved the current connection into moving armature. As its name, BLDC motor does not use brush for commutation, instead it use electronic scheme with particular mechanism.

Propulsion Motor Used

Compared to other type of motors, BLDC motor has many advantages. It can operate in high speed with more than 10000 rpm whether it is loaded or not. It also has high acceleration and fast response. The inner rotor type of the motor has a low inertia, hence can accelerate, and change direction fast. It also has high efficiency, between 85% - 90%. Additionally, it produces the highest torque and has high reliability.One fundamental thing that differs BLDC motor with common DC motor is the absence of brush in commutating process. Commutation is a process in which the phase current directed according to their sequence in order to get the output wave we wanted. Unlike in DC motor, the commutation process in BLDC motor is controlled electronically. The stator of the motor must be energized in certain sequences to make it rotate. This is important since the position of rotor depends on the sequence applied. A common sensor used to detect rotor position the Hall Effect sensor. Generally, there are three hall sensors in a BLDC motor.

Ionic Lithium LiFePO4Battery

The battery used in the car is the lithium-ionic type (See Fig.5). This battery has very good voltage and currentcharacteristic. It has higher energy density compared to other types of batteries. Furthermore, it also has a highcharging response, doesn’t have memory effect, and can be charged either it is empty or not.

Battery Charging-Discharging Test

In this test, the battery(see Fig.6) will be charged and discharged with constant current. This test is performed in order to obtain charging and discharging curve from lithium-ion LiFePO4.Battery management system on the battery will work when battery reaches state of charge 100% and depth of discharge 80% to keep the battery from overcharging and over-discharging. When battery management system works, we will obtain the upper and lower voltage limit of the battery LiFePO4.

Charging Test ResultsInitial voltage of the battery is 69.3 V. From charging characteristics curve above, it can be observed that upper voltage limit of the battery is 85 V. Charging system used is constant current/constant voltage. Battery is charged with constant current of 16 A. When the terminals reach its upper voltage limit, system will change into constantvoltage and current will slowly reduce from 16 A to its lower limit. This happens to prevent the battery from overcharged state and it makes sure that the battery is full charged. Upper voltage obtained from Laboratorium testing is equal to upper voltage limit from factory datasheet. See Fig.7 for curve of the charging process.

Discharging Test Results

Conclusion

In this paper, it has been shown that BLDC motor is one of a good choice for electric vehicle application. It has been proved that BLDC motor has a high efficiency, high torque, and good speed range. The size of this motor is also small that it can reduce the space and weight of the car. LiFePO4 battery has a capacity of 106.3 Ah on discharge current of 15 A continously for 425 minutes and it has the amount of energy of 8205 Wh. Laboratorium results show that battery capacity is 106.3 Ah while factory datasheet shows 100 Ah. This difference is caused by use of different discharge current that affect the battery capacity. This shows that the battery capacity is not changed when it leaves the factory, and the battery is still in a very goodcondition.

References

[1] Yedale, Padmaraja. “Brushless DC Motor Fundamental”, AN885, Microchip Technology Inc. 2003.[2] Linden, David. “Handbook of Batteries”, Mc Graw Hill, Third Ed. 2001.[3] http://www.pedaily.cn/Item.aspx?id=194151[4] Nguyen, John. “Safety Perfomance for Phospate Based Large Format Lithium-Ion Battery, Valence Technology. 2004.[5] Shah, Varsh, Ritesh Chaudhari, Prasanta Kundu. Performance Analysis of Hybrid Energy Storage System Using Hybrid Control Algorithmwith BLDC Motor Driving a Vehicle. IEEE.2010[6] Tashakori.A, Ektesabi M, Hosseinzadeh N. Modeling of BLDC Motor with Ideal Back-EMF for Automotive Applications . Proceedings ofthe World Congress on Engineering 2011 Vol II. IEEE 2011.